1. Field of the Invention
This invention relates to a novel organic compound and more particularly it relates to a novel organic compound capable of being used as a component constituting liquid crystal materials having a positive dielectric anisotropy value.
2. Description of the Prior Art
Liquid crystal display elements utilize the optical anisotropy and dielectric anisotropy of liquid crystal substances. Their display modes include various ones such as TN type (twisted nematic type), DS type (dynamic scattering type), guest-host type, DAP type, White-Tailor type, etc. and the properties required for liquid crystal substances used vary depending on the respective modes. For example, depending on the kinds of display elements, liquid crystal substances having a positive dielectric anisotropy value .DELTA..epsilon. are required, those having a negative one are required or those having an intermediate value therebetween are suitable. Further, it is necessary for liquid crystal substances used to exhibit a liquid crystal phase within a temperature range which is as broad as possible, and to be stable to moisture, heat, air, light, etc. At present, however, there is no single substance which satisfies all of such conditions, but several kinds of liquid crystal substances are mixed with one another or with non-liquid crystal substances, for practical use.
European patent application publication No. 0058981 A2 discloses the following compounds: ##STR6## wherein R" and R'" each represent an alkyl group of 1.about.12 carbon atoms.
The compounds (A), (B) and (C), however, have a drawback that they have a low nematic-clearing point so that the mesomorphic range of the resulting liquid crystal composition is narrowed; hence they are unsuitable for use as a component constituting liquid crystal compositions.